In Vitro Fecal Fermentation Patterns of Arabinoxylan from Rice Bran on Fecal Microbiota from Normal-Weight and Overweight/Obese Subjects

Dietary fiber and polyphenols from whole grains: effects on the gut and health improvements

Cereals are the main source of energy in the human diet. Compared to refined grains, whole grains retain more beneficial components, including dietary fiber, polyphenols, proteins, vitamins, and minerals. Dietary fiber and bound polyphenols (biounavailable) in cereals are important active substances that can be metabolized by the gut microorganisms and affect the intestinal environment. There is a close relationship between the gut microbiota structures and various disease phenotypes, although the consistency of this link is affected by many factors, and the specific mechanisms are still unclear. Remodeling unfavorable microbiota is widely recognized as an important way to target the gut and improve diseases. This paper mainly reviews the interaction between the gut microbiota and cereal-derived dietary fiber and polyphenols, and also summarizes the changes to the gut microbiota and possible molecular mechanisms of related glycolipid metabolism. The exploration of single active ingredients in cereals and their synergistic health mechanisms will contribute to a better understanding of the health benefits of whole grains. It will further help promote healthier whole grain foods by cultivating new varieties with more potential and optimizing processing methods.

Insights into the fermentation patterns of wheat bran cell wall polysaccharides using an in-vitro batch fermentation model

We aimed to study the structural characteristics and fermentation properties of wheat bran cell wall polysaccharides (CWPs). Sequential extractions of CWPs from wheat bran produced the water-extractable (WE) and alkali-extractable (AE) fractions. The extracted fractions were structurally characterized based on their molecular weight (Mw) and monosaccharide composition. Our findings revealed that the Mw and the ratio of arabinose to xylose (A/X) of AE were higher than those of WE and that the two fractions were mainly composed of arabinoxylans (AXs). The substrates were then subjected to in vitro fermentation by human fecal microbiota. As fermentation progressed, the total carbohydrates of WE were significantly more utilized than that of AE (p < 0.05). The AXs in WE were utilized at a higher rate than those in AE. The relative abundance of Prevotella_9, which can efficiently utilize AXs, was significantly increased in AE. The presence of AXs in AE shifted the balance away from protein fermentation and caused a delay in protein fermentation. Our study demonstrated that wheat bran CWPs can modulate the gut microbiota in a structure-dependent manner. However, future studies should further characterize the fine structure of wheat CWPs to clarify their detailed relationship with gut microbiota and metabolites.

Composition, Microbiota, Mechanisms, and Anti-Obesity Properties of Rice Bran

Rice is a major cereal crop and a staple food for nearly 50% of people worldwide. Rice bran (RB) is a nutrient-rich by-product of rice processing. RB is rich in carbohydrates, fibers, proteins, lipids, minerals, and several trace elements (phosphorus, calcium, magnesium, potassium, and manganese). The extraction process and storage have influenced RB extracts and RB oil's quality. The RB composition has also varied on the rice cultivars. The color of RB indicates the richness of the bioactive compounds, especially anthocyanins. γ-oryzanol, tocopherols, tocotrienols, and unsaturated fatty acids are major components of RB oil. It has been established that RB supplementation could improve the host's health status. Several preclinical and clinical studies have reported that RB has antioxidant, anticancer, anti-inflammatory, anticolitis, and antidiabetic properties. The beneficial biological properties of RB are partially attributed to its ability to alter the host microbiome and help to maintain and restore eubiosis. Non-communicable diseases (NCDs), including heart disease, diabetes, cancer, and lung disease, account for 74% of deaths worldwide. Obesity is a global health problem and is a major reason for the development of NCDs. The medical procedures for managing obesity are expensive and long-term health supplements are required to maintain a healthy weight. Thus, cost-effective natural adjuvant therapeutic strategy is crucial to treat and manage obesity. Several studies have revealed that RB could be a complementary pharmacological candidate to treat obesity. A comprehensive document with basic information and recent scientific results on the anti-obesity activity of RB and RB compounds is obligatory. Thus, the current manuscript was prepared to summarize the composition of RB and the influence of RB on the host microbiome, possible mechanisms, and preclinical and clinical studies on the anti-obesity properties of RB. This study suggested that the consumption of RB oil and dietary RB extracts might assist in managing obesity-associated health consequences. Further, extended clinical studies in several ethnic groups are required to develop dietary RB-based functional and nutritional supplements, which could serve as an adjuvant therapeutic strategy to treat obesity.

Influence of structural features and feruloylation on fermentability and ability to modulate gut microbiota of arabinoxylan in in vitro fermentation

Introduction

Arabinoxylan (AX) is a versatile polysaccharide that shows various effects in modulating gut microbiota and health. The influence of arabinoxylan carbohydrate structural feature and feruloylation on fermentability and the effect of modulation of gut microbiota of AX was not clear.

Methods

Arabinoxylans from rice bran and corn bran (RAX and CAX), and their deferulyolated counterpart dRAX and dCAX were fermented using an in vitro fermentation model. Structural information was determined based on monosaccharide composition. Gas production of fermentation products, SCFAs production, pH change, and microbiota change were measured.

Results

RAX and dRAX posessed lower A/X ratio compared with CAX and dCAX. The gas and total SCFAs production were lower in RAX and dRAX, and the butyrate production were higher in RAX and dRAX compared with CAX and dCAX. Butyrate production was lower at dRAX compared to RAX. On the other hand, butyrate production was higher in dCAX than in CAX. The microbiota shift were different for the four fibers.

Discussion

The AXs from rice have a higher A/X ratio than the AXs from maize, suggesting more branching and a more complex side chain. The structural difference was crucial for the difference in fermentation pattern. Different Bacteroides species are responsible for the utilization of rice AXs and corn AXs. Although feruloylation had a minor effect on the overall fermentation pattern, it significantly affected butyrate production and alpha diversity. dRAX promoted less butyrate than RAX, which is associated with a significantly lower amount of Faecalibacterium prausnitzi. dCAX promoted more butyrate than CAX, which may be associated with a lower amount of Bacteroides ovatus and a higher amount of Blautia in dCAX compared to CAX. The effects of feruloylation on the fermentation pattern and the resulted microbiota shift of AX varied depending on the carbohydrate structure.

Effects of arabinoxylan and chlorogenic acid on the intestinal microbiota in dextran sulfate sodium–treated mice

Dietary non-starch polysaccharides and phenolics are usually ingested at the same time. They are both regarded as prebiotics, and they regulate the intestinal microbiota through various mechanisms. Notably, however, reports of their combined or synergistic effects are rare. Arabinoxylan (AX), a polysaccharide, and chlorogenic acid (CA), a polyphenol, are widely consumed, and their effects on the microbiota have previously been discussed. In the present study, they were given to dextran sulfate sodium (DSS)–treated mice, separately and together, and the intestinal microbiota were investigated by high-throughput sequencing. The data showed that CA attenuated body weight loss, colon shortening, and histological damage in DSS-treated mice, while neither AX nor the AX+CA combination exhibited any ameliorating potential. AX+CA had less of a modulating effect on intestinal microbiota profiles than did CA. AX+CA administration increased the relative abundance of Flavonifractor, Coprobacillus, and Clostridium_XlVa, and decreased the abundance of Robinsoniella and Lactobacillus. Compared to AX and CA, AX+CA contributed to a more complicated shift in the biological functions of the intestinal microbiotaAX seemed to weaken the beneficial effects of CA, at least in the present experimental model of DSS-induced colitis. The combined effects and mechanisms of dietary polysaccharides and phenolic compounds on the intestinal microbiota and on overall health still need to be further investigated.

Diet-Related Changes of Short-Chain Fatty Acids in Blood and Feces in Obesity and Metabolic Syndrome

Obesity-related illnesses are one of the leading causes of death worldwide. Metabolic syndrome has been associated with numerous health issues. Short-chain fatty acids (SCFAs) have been shown to have multiple effects throughout the body, both directly as well as through specific G protein-coupled receptors. The main SCFAs produced by the gut microbiota are acetate, propionate, and butyrate, which are absorbed in varying degrees from the large intestine, with some acting mainly locally and others systemically. Diet has the potential to influence the gut microbial composition, as well as the type and amount of SCFAs produced. High fiber-containing foods and supplements increase the production of SCFAs and SCFA-producing bacteria in the gut and have been shown to have bodyweight-lowering effects. Dietary supplements, which increase SCFA production, could open the way for novel approaches to weight loss interventions. The aim of this review is to analyze the variations of fecal and blood SCFAs in obesity and metabolic syndrome through a systematic search and analysis of existing literature.

Effects of Zymosan on Short-Chain Fatty Acid and Gas Production in in vitro Fermentation Models of the Human Intestinal Microbiota

In this study, the effects of zymosan (HG, hydrolyzed glucan) on the structure and metabolism of fecal microbiota in Chinese healthy people was investigated by an in vitro simulated intestinal microecology fermentation model. We found that HG significantly regulated fecal microbiota composition, including the increase of Bifidobacterium, Faecalibacterium, Prevotella and the decrease of Escherichia-Shigella. Moreover, HG significantly increased the total production of short chain fatty acids (SCFAs) and gases, in which the production of Acetic acid, Propionic acid, CO₂, and H₂ significantly increased while the production of Isovaleric acid and NH₃ significantly decreased. Additionally, the supplement of HG showed certain differences in the regulation of microbiota from four groups. HG significantly increased the relative abundance of Bifidobacterium and significantly decreased the relative abundance of Escherichia-Shigella excluding the older men group. Meanwhile, and the relative abundance of Lactobacillus was significantly increased in young populations. And the relative abundance of Bacteroides was significantly decreased only in the young women. Furthermore, HG significantly increased H₂ concentration only in older men. These findings suggest that HG, as a new generation of prebiotics, could regulate the structure of fecal microbiota and its metabolites in a better direction, but when HG participates in precision nutrition formula, it may be necessary to consider the differences in the utilization of different populations.

Arabinoxylan from rice bran protects mice against high-fat diet-induced obesity and metabolic inflammation by modulating gut microbiota and short-chain fatty acids

Rice bran is an important by-product of the milling industry. Arabinoxylan extracted from rice bran (RAX) is available in large quantities and is structurally different from other arabinoxylans from cereals. The anti-obesity effects of RAX and the role of microbiota have not been studied. In this work, we investigated the beneficial effects of RAX in C57BL/6J mice fed a high-fat diet (HFD). We found that supplementation of RAX significantly ameliorated HFD-induced obesity. RAX decreased HFD induced lipid accumulation and regulated genes related to hepatic fatty acid metabolism. Regulated lipid metabolism is associated with reduced systemic inflammation as indicated by TNF-α and IL-6. RAX normalized the gut microbiota and its major metabolites short-chain fatty acids (SCFAs). RAX restored the alpha diversity of the gut microbiota and increased the relative abundance of anti-inflammatory bacteria including Bifidobacterium and Akkermansia. RAX decreased pro-inflammatory bacteria including Anaerotruncus, Helicobacter, Coprococcus, and Desulfovibrio. Our results suggest that systemic inflammation bridges to the gut microbiota through LPS and SCFAs. RAX modulates the gut microbiota and SCFA production in the large intestine, thereby reducing systemic inflammation and ameliorating obesity. In brief, RAX prevented obesity through a mechanism related to the modulation of the microbiota and its metabolites.